Sperical permanent diamond lap and method of use

ABSTRACT

A spherical diamond lap for producing spherical cavities of gas bearing quality for gyros in which the spherical diamond lap has diamond particles bonded to the outer surface thereof to perform the cutting action of the spherical cavities within the gas bearing gyro. The spherical diamond lap is rotated through particular strokes to cut precision cavities.

United States Patent [191 Widner et al.

[451 Aug. 27, 1974 1 SPERICAL PERMANENT DIAMOND LAP AND METHOD OF USE [75] Inventors: Rayburn K. Widner, Arab; Aubrey Rodgers, Huntsville, both of Ala.

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

[22] Filed: Nov. 6, 1973 [21] Appl. No.: 413,407

12/1963 Hoffman 51/284 X 11/1966 Abernathy 51/204 ABSTRACT A spherical diamond lap for producing spherical cavig 51/204 5 z id ties of gas bearing quality for gyros in which the spher- I g i [58] new of 51/204 205 241 241 outer surface thereof to perform the cutting action of 51/241 290 the spherical cavities within the gas bearing gyro The spherical diamond lap is rotated through particular [56] References C'ted strokes to cut precision cavities.

UNITED STATES PATENTS 7 243,343 6/1881 Gates 5l/29O UX 5 Claims, 2 Drawing Figures 34- Oil- 493 9 SPERICAL PERMANENT DIAMOND LAP AND METHOD OF USE BACKGROUND OF THE INVENTION Conventional laps for producing spherical cavities of gas bearing quality such as in gas bearing gyros use loose abrasive between a spherical lap and spherical surfaces on the spherical cavity. With'this arrangement, the abrasive particles are free to move on both the lap surface and the speherical work piece surfaces being lapped. The abrasive particles simultaneously reduce in size both the lap and the work piece surfaces. Therefore, with this conventional lap, it is impossible to produce spherical cavities identical insize or predict the exact size cavity that will be produced; Also, since the lap is reduced in size by the lapping action, a lap cannot be used repeatedly due to the change in size of the lap.

Therefore, it is an object of this invention to provide a permanent spherical shaped diamond lap that can be used to mass produce spherical cavities for spherical bearing gas gyros.

Another object of this invention is to produce a permanent spherical shape diamond lap that can be used to duplicate many cavities within critical dimensional tolerances of size and configuration required for spherical gas bearing and thus greatly improved performance from one gyro relative to another and simultaneously increase acceptable gyro output.

A further object of this invention is to provide a permanent diamond lap that can be used in making spherical cavities of critical dimensions by rotating the spherical lap relative to the surfaces to be lapped and by flushing away particles of metal removed by the diamond cutting edges using a continuous stream of diamond lap lubrication.

A still further object of this invention is to use a diamond lap that utilizes the method step in producing the spherical cavity of rotating the diamond lap relative to the work pieces by moving the spherical lap in both a figure 8 stroke and also by a or round type stroke.

SUMMARY OF THE INVENTION In accordance with this invention, a spherical permanent type lap is provided in which the outer surface of the spherical lap has diamond particles embedded therein to provide diamond cutting edges. The diamond particles are bonded to the spherical surface of the lap by anodizing. The spherical diamond lap is used in a method to produce spherical cavities within critical dimensional tolerances by placing the spherical lap between halves of a work piece to be lapped such as those of a spherical air bearing gyro. The spherical diamond lap is first placed into one half of a premachined spherical cavity, and then the second half with a premachined spherical cavity is placed in enclosing relation to the spherical diamond lap. The spherical diamond lap has a plurality of holes therethrough to actuate the spherical diamond lap relative to the work pieces. A steel pin is inserted into one of the holes in the spherical diamond lap exposed at either end of the work piece through ports located at the ends of the work piece. The pin is then actuated by hand in a figure 8" configuration for several strokes and then changed to a 0" or round stroke. The pin is then moved to another hole in the spherical diamond lap and alternated between the two strokes until lapping is completed. As the lapping is taking place, the two halves of the work piece are gently pressed together as the spherical diamond lap is in motion. Also, as the spherical diamond lap is BRIEF DESCRIPTION OF THE DRAWINGS In the drawing: FIG. 1 is a perspective view partially in section of a spherical diamond lap according to this invention, and

FIG. 2 is a view partially in section illustrating the method of using the sphericaldiamond lap.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, a permanent spherical diamond lap 10 is illustrated that is made up of an aluminum spherical core 12 with diamond grit particles 14 pressed or rolled into the pores of spherical core 12 and with an anodized bonding layer 16 that bonds diamond grit 14 to the surface of spherical core 12. Core 12 has a plurality of approximately 28 through bores 18 for actuating the spherical diamond lap relative to the surfaces to be lapped. Spherical core 12 is finished to the particular spherical accuracy desired and then diamond grit 14 is pressed or rolled into the pores of the aluminum core 12 and finallythe outer surface is anodized to firmly secure the diamond grit in the pores of member 12. It is to be understood that diamond grit 14 can be varied in size depending upon the coarseness of the cut desired on the surfaces to be lapped. It has been found that a diamond grit size of 600 or 30 microns or less works well for coarse lapping and a diamond grit size of 1,200 or 15 microns or less works well for finer cutting. The hard anodic coating 16 has a thickness of 0.001 inch or more to firmly secure diamond grit 14.

lapping operation, the following method has been found to be very successful. First, spherical diamond lap '10 is placed into one half of machined spherical cavity 20, then the second half 26 with spherical cavity 22 is put in place to enclose the lap except at the large exhaust ports 30 and 32 of spherical halves 24 and 26 respectively. Next, steel pin 28 is inserted into one of holes 18 of the lap exposed at either end of the rotor. To start the lapping operation, steel pin 28 is actuated by hand in a motion of a figure 8" for several strokes and then changed to a 0 or round stroke. Alternate between these two strokes during the lapping operation. While the lapping motion is taking place, the halves are held or pressed together gently to the spherical lap as it is in motion. Also, a small continuous stream of filtered diamond lap lubrication, such as kerosene, is used to flush away particles of metal removed by the diamond cutting edges of the spherical lap. As the motion of steel pin 28 is continued, occasionally change the steel pin to a different hole 18 in the lap and proceed as before with the motion of the spherical diamond lap relative to the cavities that are being lapped. This procedure is continued until mating surfaces 34 and 36 of the rotor make lateral contact and the spherical diamond lap hascut itself free.

By using the diamond spherical lap as described hereinabove and by employing the diamond spherical lap in a method as set forth hereinabove, lapped spherical cavities of precision dimension can be made and duplicated using the same permanent spherical diamond lap.

We claim: 1. A spherical diamond lap comprising an aluminum sphere, diamond grit mounted in pores at the surface of said aluminium sphere, an anodizing layer over the said aluminum sphere.

2. A spherical diamond lap as set forth in claim 1, wherein said diamond grit is of a size of about 600 to about 1,200.

3. A spherical diamond lap as set forth in claim 2, wherein said bores are 28 in number.

4. The method of making a spherical cavity in two mating members, such as halves of a gyro, comprising placing a spherical diamond lap between halves of the gyro that have generally spherical cavities therein, pressing the two halves against the spherical diamond lap, maintaining pressure on the two halves of the gyro, rotating said spherical diamond lap by a pin in a bore through said spherical diamond lap first in a figure 8 direction for several strokes and then in a 0 stroke, next moving the pin to other bores through the spherical diamond lap and repeating the figure 8" and the 0 strokes of the spherical diamond lap with respect to each bore, simultaneously supplying a stream of dia-' mond lap lubrication to the spherical diamond lap and the surfaces being lapped, and continuing the motion of the spherical diamond lap until mating surfaces on the halves make lateral contact and the spherical diamond lap has cut itself free.

5. The method of making a spherical cavity in two mating members as set forth in claim 4, wherein said spherical diamond lap has grit of a size of about 600 to about 1,200 and said grit has been bonded to the spher- 

1. A spherical diamond lap comprising an aluminum sphere, diamond grit mounted in pores at the surface of said aluminium sphere, an anodizing layer over the outer surface of said sphere and securing said diamond grit in bonded position within said pores of said aluminum and a plurality of uniform diameter bores through said aluminum sphere.
 2. A spherical diamond lap as set forth in claim 1, wherein said diamond grit is of a size of about 600 to about 1,200.
 3. A spherical diamond lap as set forth in claim 2, wherein said bores are 28 in number.
 4. The method of making a spherical cavity in two mating members, such as halves of a gyro, comprising placing a spherical diamond lap between halves of the gyro that have generally spherical cavities therein, pressing the two halves against the spherical diamond lap, maintaining pressure on the two halves of the gyro, rotating said spherical diamond lap by a pin in a bore through said spherical diamond lap first in a figure ''''8'''' direction for several strokes and then in a ''''o'''' stroke, next moving the pin to other bores through the spherical diamond lap and repeating the figure ''''8'''' and the ''''o'''' strokes of the spherical diamond lap with respect to each bore, simultaneously supplying a stream of diamond lap lubrication to the spherical diamond lap and the surfaces being lapped, and continuing the motion of the spherical diamond lap until mating surfaces on the halves make lateral contact and the spherical diamond lap has cut itself free.
 5. The method of making a spherical cavity in two mating members as set forth in claim 4, wherein said spherical diamond lap has grit of a size of about 600 to about 1,200 and said grit has been bonded to the spherical lap by anodizing. 